<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>

    //数组求和
    // const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9]
    // const getSum = arr.reduce((sum, item) => {
    //   return sum += item
    // }, 0)
    // console.log(getSum)

    //拼接字符串
    // const arr = ['1', '2', '3', '4', '5', '6', '7', '8', '9']
    // const getStr = arr.reduce((str, item) => {
    //   return str += item
    // }, '')
    // console.log(getStr)
  </script>
</body>

</html>